FIG. 1 illustrates a normal locking arrangement comprising a lock unit 4 and counter part 5. Usually, the lock unit is installed in a door 1 and the counter part 5 is installed in the door frame 2, but other ways of installing are also possible. Latch 6 is moved (pushed or turned) from the lock unit to the counter part, i.e. the striker plate. In the example of FIG. 1 the striker plate is installed in the door frame, and it can be seen that upon locking the door the latch is pushed into a hole in the door frame and the striker plate.
The necessary movement of the latch must be sufficient to keep the door closed in, for example, cases of vandalism, despite the door clearance, i.e. the gap 8 between the door and the frame, the clearance fluctuating on the basis of the door type, the installation tolerances, temperature etc. Typically, the door clearance is between 1 and 5 mm. Usually, the movement of the latch is 14 mm, or in a door of a higher security rating, even 20 mm. The latch is moved by, for example, a key, an electric motor or a button.
Usually, the movement of the latch is transverse to the movement of the door (direction of opening and closing), so that the force exerted on the door upon opening, such as a sealing force caused by the seal 3 or pushing the door, will make the movement of the latch considerably more difficult, because there is friction between it and, for example, the striker plate. There is friction in the inner components of the lock as well, between 7 the latch and other components of the lock unit. This means also that when opening the lock by means of a key or an electric motor, plenty of force is needed to overcome the forces and friction, if any.
Additionally, during burglary, considerable bending stress is exerted on the latch, so that the components will have to be massively dimensioned.
Because of the great force needed to move the latch and the relatively large movement of the latch, the energy needed is usually too large for battery operation. Additionally, powerful and expensive motor gearings are needed. As far as energy consumption is needed, panic exit regulations (standard EN 1125) must be considered, according to which a locked door must be capable of being opened, even though a transverse force of 1000 Newton is exerted in the central part of the door. Fulfilling this requirement using currently known solutions is very difficult and expensive.
Further, a number of sensors has previously been used for sensing the state of the object to be locked, such as a door. Separate sensors have been used for indicating, for example, whether the door is open, the locking locked and the locking open. The aim of the present invention is to reduce the above-mentioned problems of the prior art. The aim is achieved as disclosed in the claims.